Wireless communication systems are widely used to provide various types of communications. For example, voice and/or data are provided by the wireless communication systems. A conventional wireless communication system provides multiple users with one or more shared resources. For example, the wireless communication system can use various multiple access schemes such as code division multiple access (CDMA), time division multiple access (TDMA), and frequency division multiple access (FDMA).
Orthogonal frequency division multiplexing (OFDM) uses a plurality of orthogonal subcarriers. Further, the OFDM uses an orthogonality between inverse fast Fourier transform (IFFT) and fast Fourier transform (FFT). A transmitter transmits data by performing IFFT. A receiver restores original data by performing FFT on a received signal. The transmitter uses IFFT to combine the plurality of subcarriers, and the receiver uses FFT to split the plurality of subcarriers. According to the OFDM, complexity of the receiver can be reduced in a frequency selective fading environment of a broadband channel, and spectral efficiency can be increased when selective scheduling is performed in a frequency domain by using a channel characteristic which is different from one subcarrier to another. Orthogonal frequency division multiple access (OFDMA) is an OFDM-based multiple access scheme. According to the OFDMA, efficiency of radio resources can be increased by allocating different subcarriers to multiple users.
In the wireless communication systems, one or more cells are included in the coverage of a base station (BS). A plurality of user equipments (UEs) can be located in one cell. The BS provides a data service to the UEs located in the cell. Data transmitted by the BS to the UEs may be unicast data, multicast data, or broadcast data. The unicast data is a message transmitted to a specific UE. The multicast data is a message transmitted to a specific UE group. The broadcast data is a message transmitted to all UEs. The broadcast data includes a cell specific message limited to one cell and a multi-cell specific message common to a plurality of cells. The multi-cell specific message can be referred to as a single frequency network (SFN) message.
When a UE initially accesses to a new cell, the UE performs downlink synchronization and receives system information of a network to be accessed. The BS transmits a preamble according to a predetermined period so that the UE can perform the downlink synchronization. The preamble is a specific sequence provided for each of a plurality of BSs. The preamble may include information such as a cell identifier (ID). In a multiple antenna system using a plurality of antennas, the preamble can be transmitted using difference sequences for respective transmit antennas of the BSs. By using the preamble, the UE can perform downlink synchronization and channel estimation. The system information is necessary information which must be known to the UE to communicate with the BS. The system information can be transmitted using a cell specific message or a multi-cell specific message.
The multi-cell specific message is a message commonly transmitted from a plurality of BSs. The UE performs decoding by combining the multi-cell specific messages of the respective BSs. To combine the multi-cell specific message of the respective BSs, the UE has to estimate a channel of each multi-cell specific message and then compensate for a channel value. Estimating of the multi-cell specific messages of the respective BSs and compensating for the channel value may produce a large overhead in a process of decoding the multi-cell specific messages.
Accordingly, there is a need for a method capable of effectively transmitting and/or acquiring a plurality of multi-cell specific messages.